1. Field of the Invention
This invention relates to a film reader equipped with a reflecting type screen.
2. Description of the Prior Art
Film readers, which enable observation of an enlarged image projected on a screen of the image recorded on a microfilm, are classified into two kinds according to the type of the screen to be used. One kind of film readers uses the so-called transmitting type screen comprising a transparent glass plate or synthetic resin plate provided with a photo-diffusion layer on one surface thereof. This kind of reader is called a transmitting type reader by which an image on a microfilm is projected on one side of said transmitting type screen and a light image transmitted the screen is observed from the opposite side of the screen. The other kind of reader is called a reflecting type reader which uses the so-called reflecting type screen similar to a movie screen. An image on a film is projected on said screen, and a light image reflected by the screen is observed from the same side of the projecting surface. The reflecting type reader is more attractive than the transmitting type reader as it is easier to see a projected image than a transmitted one. In the former type film reader, an observer is able to see a projected image well enough to read printed matter such as a book, etc. However, the reflecting type film reader does not always give the most suitable projected image, because it is inevitable that the contrast of a projected image will be deteriorated by peripheral external light other than an image projecting light incident on the screen, and further there has been no satisfactory device to reduce the influence of such external light. In the conventional reflecting type film reader, a large aperture for observation is provided at a portion of a square housing and a screen provided within the housing is observed through said aperture, so that when the reader is used in a light place, a light external of the reader comes into the housing through the aperture and impinges on the screen, and this incident light goes toward the eyes of the observer, who will then observe both of the image light and this peripheral light. As a result, the contrast of the image becomes significantly degraded and the brightness of the image becomes non-uniform because the light before the screen and inside of the screen on which the peripheral light impinges are different from each other.
According to the conventional reflecting type film readers, there have been proposed the combination of a screen having a high light diffuse-reflection characteristic with an external light control filter; or a high brightness screen having a specific uneven surface of a dotted or line form to reflect a part of the light to a certain direction; or the light brightness screen having a curved screen surface so as to keep the intensity of the light reflected by the screen high relative to the external light. However, the screen combined with a filter is limited in its effect because the intensity of an image projection light is limited, and an obtained image is degraded due to a ghost produced by a light reflected by the filter surface. And the high brightness screen produces partially bright points so that a strong glittering phenomenon occurs, which causes deterioration of the image quality and fatigue of the observer's eyes. These disadvantages are counted as defects in the conventional reflecting type microfilm readers although they are easy to observe.